I too can sometimes take a few minutes to get things together in my head. Sunday was a good example.
I was at my Santa kids shoot (using strobes). During a quiet period, I was showing my second shooter a few speedlight tricks. Bouncing, and so on.
But.. the speedlight was not working! Every time I fired, I got dark pictures. I started at 400-40-4 (i.e. at 400 ISO, 1/40th second, f/4: the Willems 444 Rule for indoors mixed light flash), and then got dark pictures -background good as per 444, but flash part dark. Huh?
- First thing to do in these cases: Turn your flash to MANUAL mode, at full power (1/1). That shows you if you have enough power available at all – if the picture comes out overexposed, all is well and you have enough power available, so the problem must be a metering or setting problem. And that was the case: bright pictures, way overexposed. So there was enough power available: it was simply a TTL metering problem or hardware problem.
- Second thing to do: check that metering is not “spot”; check all other camera settings, like flash exposure compensation; and verify that you are not sdhooting a very dark or very bright subject. Nope, no problems there.
- Third thing to do: reset camera and flash by powering down and up; remove flash, clean contacts; reconnect; turn it all on again. Did not work.
- Fourth thing to do: try a different flash. Same problem!
This is where I was flummoxed for a few moments. Huh? I do not like surprises like this.
Until it hit me. D’oh! Each time I fired, my speedlight’s preflash (that is how TTL flash works) was setting off the nearby second strobe (which uses a cell to detect when it must fire). So the TTL measurement got way too much light back – hence the flash was told to fire at ultra-low power.
The solution was simple: turn off the slave cell on the strobe. Now, no extraneous flashes, and all was well.
So remember: Accidentally co-firing strobes can leave your pictures extremely underexposed – or extremely overexposed (whether over ort under is unpredictable because it depends on the exact timing of the strobe flash).
Of course I knew this, but I was momentarily not thinking. Goes to underscore: all photography is always problem solving, and if you take it logically the answer wil come to you!